﻿<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" >
<head>
    <title>无标题页</title>
    <style type="text/css">
    .day
    {
    	background-color:White;
    }
    .night
    {
    	background-color:Black;
    }
    </style>
    <script type="text/javascript">
    function switchLight()
    {
        if(document.body.className == "day")
        {
            document.body.className = "night";
            document.getElementById("lightBtn").value = "开灯";
        }
        else
        {
            document.body.className = "day";
            document.getElementById("lightBtn").value = "关灯";
        }
    }
    </script>
</head>
<body class="day">
<input type="button" value="关灯" id="lightBtn" onclick="switchLight();" />
</body>
</html>
